The present invention relates to an information system, and method, for encrypting and holding personal information and secret information and preventing an information leak to a third person.
The spread of high-performance, highly portable computers such as laptop personal computers (PCs) and pen-input PCs results in increased occasions to use computers for the purpose of business in various places other than the office such as the destination of one's business trip. The spread of such portable computers is poses the problem of information leaks due to theft and loss of computers.
On the other hand, computers such as PCs have come into wide use in homes as well with the advance of multimedia. In the case of such a computer for home, the computer is often shared by the family and the personal information protecting function is being needed.
Because of such portability of computers and penetration of computers to homes, there is a need for the security function at the end user level to prevent a leak of secret information and personal information relating to business.
As for the security function coping with these needs, the file encryption function for encrypting secret information files and personal information files by using an encryption key and protecting them from being accessed by a third person having no encryption key is known as an effective technique. For example, the RSA public key is disclosed in U.S. Pat. No. 4,405,829.
In the conventional file encryption function, an encryption key kept secret from a third person was used for encryption processing. At the time of file encryption and decryption, therefore, preparation manipulation such as encryption key opening manipulation using password input is necessary for the user to manage the encryption key. Furthermore, management of the encrypted file has been entrusted to the user. For example, it has been necessary for the user to remember on the user's own responsibility which encryption key has been used to encrypt the file in order to decrypt the file afterwards. Thus the conventional file encryption function had the following problems. Expert knowledge is typically neccessary. Because of complicated manipulation, manipulation was difficult for the end user, and the end user could not easily use the conventional file encryption function. In general, therefore, a high-degree security function such as file encryption has been intended for the user performing certain special business.